Steady and pulsating flow characteristics in straight tubes with and without a lateral circular protrusion

Flow characteristics in straight tubes with and without a lateral circular protrusion had been investigated using Particle Image Velocimetry over a range of Reynolds numbers from 400 to 1400, and at Womersley number of 65. The practical interest of the flows considered lies mainly in blood flows through arteries with saccular aneurysm. Both steady and pulsating flow experiments had been conducted. It was found that under the steady flow conditions, a recirculating vortex would be formed inside the circular protrusion. The maximum strength of the vortex would be as low as 10% of the bulk mean velocity in the main tube at the highest Reynolds number tested (i.e. at 1400). Under the pulsating flow conditions, the vortex appeared and disappeared at different phase of a cycle. The sequence was only punctuated by quasi-inviscid flow behavior. The steady flow results only resembled those of the pulsating ones for about 1/10 of the time at each cycle.